Different portable electric drills having different specialized functions, such as drilling, hammer drilling, screwdriving etc., are well known. However, due to the different mechanisms needed to perform these different specialized functions, each of these different portable electric tools is usually individually designed and requires a separate production arrangement to manufacture.
Some of these specialized tools may be provided with a two-speed gear box to improve their performance when operating upon different materials or when performing different tasks. However, the incorporation of known two-speed gear boxes further complicates the manufacture of these tools and has tended to increase the differences in construction, and therefore manufacture, between such tools designed to perform specialized functions which are different from tool to tool.
Further, some of the two-speed gear transmission arrangements that have been used involve rather complicated or individual assembly procedures, and/or have deficiencies concerning gear changing, particular when the tool is running. As a consequence, there has been a tendency to specifically design different two-speed gear boxes for incorporation in different specialized tools.